Rapid high-pressure microwave thermal decomposition system, capsule and method for using same

ABSTRACT

Carbon dioxide, such as may be used for a carbonated beverage, is produced by microwave thermal decomposition of a starting material. An apparatus for the process includes a microwave generator, a microwave chamber, a capsule received in the chamber containing starting material(s) and one or more channel(s) for recovering CO 2  generated in the process.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/931,720, filed Jan. 27, 2014, which is incorporatedby reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is directed to the production of carbon dioxide underpressure, for beverages and the like, by thermal decomposition ofvarious starting materials utilizing radio frequency (RF) energy.

2. Description of the Prior Art

Various methods and apparatuses for using microwaves to effect thermaldecomposition are known in the prior art. Representative examplesinclude WO 2013/070095 which describes a microwave heating or reactionapparatus for use for example in pyrolysis of organic waste. EP 343 673A1 describes a process for the manufacture of extra light soda, in whichsodium carbonate is treated with microwave energy. The prior art has notdisclosed a method or apparatus for production of carbon dioxide usingmicrowave thermal decomposition.

SUMMARY OF THE INVENTION

In one aspect the invention is a thermal decomposition systemcomprising: an RF energy generator; an RF antenna or electrode connectedto the RF generator; a capsule chamber having a sealable opening adaptedto receive and retain at least one capsule comprising a thermallydecomposable material and to withstand a defined pressure evolving inthe capsule; and at least one channel having a first end opened to thecapsule and a second end connected to a pressure valve. Thus,application of RF energy to the thermally decomposable material in thecapsule causes thermal decomposition which evolves gas.

In specific embodiments, the invention is a thermal decomposition systemfor carbon dioxide production (and corresponding method) comprising: amicrowave generator; a microwave antenna connected to the microwavegenerator; a capsule containing sodium bicarbonate; a capsule chamberhaving a sealable opening adapted to receive and retain the capsule andto withstand a defined pressure evolving in the capsule; and at leastone channel having a first end opened to the capsule and a second endconnected to a pressure valve; wherein the microwave generator generatesmicrowave energy applied to the capsule sufficient to cause thermaldecomposition of the sodium bicarbonate to evolve carbon dioxide.

In another aspect, the invention is directed to a capsule for a thermaldecomposition system, comprising a shell enclosing a cavity, and atleast a first compartment in said cavity containing a thermallydecomposable material. In embodiments, the capsule further comprises afilter to prevent the thermally decomposable material and byproducts ofthermal decomposition from being expelled from the capsule duringthermal decomposition of the material.

In another aspect, the invention is a method for producing carbondioxide which comprises providing an RF energy generator and an RFantenna or electrode connected to the microwave generator and enclosingin a capsule in a capsule chamber a thermally decomposable startingmaterial that evolves carbon dioxide upon thermal decomposition. Thecapsule chamber has a sealable opening adapted to receive the capsule,and the capsule is adapted to withstand a predetermined pressure evolvedduring the thermal decomposition. A channel is provided having a firstend opened to the capsule and a second end connected to a pressurevalve. Radio frequency energy is generated with the RF energy generatorto heat the thermally decomposable material and evolve carbon dioxideunder pressure.

In another aspect, the invention involves modelling the thermodynamicsof thermal decomposition using both theoretical microwave powerabsorption coefficients and empirical results to obtain an optimalsodium bicarbonate:water ratio for a given mass of sodium bicarbonateand microwave frequency. From these data, system elements are developedto yield maximum carbon dioxide extraction from the thermaldecomposition process in the minimum amount of time.

Embodiments of the present invention provide a unique rapid heatingsystem, composed of a radio frequency power source and a custom designedcavity. The system is designed for heating thermally decomposablematerials, such as sodium bicarbonate powder, at a high pressure toextract carbon dioxide efficiently and rapidly.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter regarded as the invention is particularly pointed outand distinctly claimed in the concluding portion of the specification.The invention, however, both as to organization and method of operation,together with objects, features, and advantages thereof, may best beunderstood by reference to the following detailed description when readwith the accompanying drawings in which:

FIGS. 1A, 1B, 1C and 1D are schematic illustrations of thermaldecomposition systems according to some embodiments of the presentinvention;

FIGS. 2A and 2B are schematic illustrations of other embodiments of athermal decomposition system.

FIG. 3 is a schematic illustration of a system according to anembodiment of the present invention having a capsule chamber adapted fortwo capsules;

FIG. 4A is an illustration of a system according to embodiments of thepresent invention for simultaneous thermal decomposition and waterheating;

FIG. 4B is an additional illustrations of high pressure microwavethermal decomposition systems according to some embodiments of thepresent invention;

FIGS. 5A, 5B, 5C, 5D and 5E are exemplary illustrations of capsulesaccording to embodiments of the present invention;

FIG. 6 is a flowchart of a method for thermal decomposition of amaterial according to embodiments of the present invention.

FIG. 7 is a graphic showing total dissipation of an ionic solution ofsodium bicarbonate as a function of temperature and ionic concentrationat fixed microwave frequency.

FIG. 8 is a graphic showing sodium bicarbonate solution microwavedissipation as a function of water content for fixed microwavefrequency.

FIG. 9 is a graphic showing reaction time as a function of water contentfor the thermal decomposition of sodium bicarbonate in the range of 20°C. to 150° C.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the figures have not necessarily been drawn to scale.For example, the dimensions of some of the elements may be exaggeratedrelative to other elements for clarity. Further, where consideredappropriate, reference numerals may be repeated among the figures toindicate corresponding or analogous elements.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the invention.However, it will be understood by those skilled in the art that thepresent invention may be practiced without these specific details. Inother instances, well-known methods, procedures, and components have notbeen described in detail so as not to obscure the present invention.

Preferred embodiments according to the invention utilize RF energy witha frequency of 3 KHz to 300 GHz, which also includes microwave (MW)energy, having a frequency of 300 MHz to 300 GHz. The examples hereindirected to heating with MW energy should not be deemed to limit theinvention. Likewise, Examples herein using commercially available MWenergy producing elements, operating at frequencies of 2.4-2.5 GHz,should not be construed as limiting the invention

“Wet powder” is understood to refer to a powder mixed with a liquid thatabsorbs MW energy. Such liquid includes without limitation water, oil,alcohol or other solvent, water-alcohol solution, etc. The wet powdermay contain SBC and water, in which case the SBC powder may be partiallydissolved in water. “Thermal decomposition” refers to a chemicalreaction that evolves gas upon heating. Thermal decomposition includes,but is not limited to, the thermal decomposition of sodium bicarbonateto evolve carbon dioxide.

Thermal decomposition based on microwave (MW) absorption heating is acomplex dynamic process. The microwave absorption dependent parametersall vary during the process and may lead to unwanted results, such asthermal runaway and deterioration of decomposition efficiency. On theother hand, maximum microwave absorption during the entire process maybe achieved by prior knowledge of the variation in the main processparameters, together with control of the component ratio of thecomponents being subjected to microwave heating energy.

In general, MW energy absorption in materials is impacted by two mainmechanisms of dissipation—dielectric and ion conduction. The totaldissipation component, which is the relative imaginary part of thematerial permittivity (∈″) is the sum of the dielectric absorptioncomponent (∈″_(d)) and the ionic dissipation absorption (∈″_(c)):∈″=∈″_(d)+∈″_(c)  (1)

Dielectric absorption is caused by molecule dipoles which tend to rotatewhen introduced into the alternating electric field of MW radiation.Dielectric absorption is a function of the angular frequency of theelectric field (ω), molecule dipole relaxation time (τ) and thedifference (∈_(Δ)) between the material permittivity value at zeroangular frequency to the value at infinite angular frequency:

$\begin{matrix}{ɛ_{d}^{''} = \frac{ɛ_{\Delta}{\omega\tau}}{1 + {\omega^{2}\tau^{2}}}} & (2)\end{matrix}$

The ionic conduction is caused by mobile dissolved ions which act asfree charged particles which oscillate along the electric field of theMW radiation. Ionic dissipation absorption is equal to the ratio betweenthe electrical conduction (σ) and the product of the vacuum permittivity(∈₀) and electric field angular frequency:

$\begin{matrix}{ɛ_{c}^{''} = \frac{\sigma}{ɛ_{0}\omega}} & (3)\end{matrix}$

Both mechanisms contribute to object heating as a result of dipolemovement and intermolecular friction forces. The heating power density(P) absorbed in the material depends on the average electric fieldintensity (E), material total dissipation (∈₀ ∈″) and electric fieldangular frequency (ω):P=ω∈₀∈″E²  (4)

MW absorption varies strongly during the thermal decomposition process,due to the changes in material temperature, number of dipoles (watercontent) and ion concentration. Using the sodium bicarbonate(“SBC”)-water system as an example, FIG. 8 illustrates the dependence ofthe total dissipation of ionic solution as a function of temperature andionic concentration at fixed MW frequency.

A system according to embodiments of the present invention, utilizesdielectric heating to heat the target material (e.g. wet SBC powder)above 150° C., a temperature range at which efficient thermaldecomposition takes place. Above 50° C., sodium bicarbonate (NaHCO₃)transforms into 63.1% sodium carbonate (Na₂CO₃), 10.7% water (H₂O) and26.2% carbon dioxide (CO₂), by mass. The reaction rate increasesexponentially with temperature, and is optimal in terms of decompositionrate around 200° C., where more than 90% of the original material isdecomposed within one minute. At higher temperatures additionalprocesses set in, and carbon dioxide production decreases.

Using an electromagnetic field simulation software, a microwave cavitywas designed with compact dimensions compared to a typical microwave. Inthis design, the position and geometry of the reaction chamber wereoptimized to reduce reflections back into the microwave generator (e.g.magnetron) source and to obtain homogeneous heating across the chamber.

Optimizing MW radiation absorption was achieved by focusing performanceon heating wet powder, allowing the liquid in the powder to generate andconvey heat across the powder in the chamber as efficiently as possible.It was discovered that when the water molecules transform state fromliquid to vapor, the efficiency of heating of the powder drops. To keepthe absorption of microwaves in the cavity high even at temperaturesabove 100° C., the container was sealed in a pressure tight mannerduring heating and thus the water was kept in a liquid state. Thisenables an efficient transfer of heat between the water and powder, andreduces water loss substantially.

The magnetron was tightly mounted on the microwave cavity, to eliminatemicrowave energy radiation from leaking out. The system that wasdeveloped and used during the measuring of the performance of the systemand method according to embodiments of the present invention complieswith radiation safety regulations when operated with a standard 1 kWmagnetron.

The microwave cavity was characterized using an electromagnetic fieldsimulator, and using the Agilent 5230A network analyzer.

In the simulator, the reflection coefficient S₁₁ in the frequency range2.4-2.5 GHz for a water filled reaction chamber was extracted (thedielectric function of SBC at these frequencies is unknown). Since thereis no leakage from the system and since there is no absorption in otherparts of the system, the amount of power absorbed may be directlycalculated from the reflection coefficient. To keep the magnetron fromdamage and long-term deterioration, it is advised to keep the reflectedpower below 5%. In the tested design, the reflected power was in therange of 1-3% within the uncertainty range of the magnetron frequency(2.4-2.5 GHz).

The device was experimentally tested at low power using a networkanalyzer (Agilent 5230A), measuring the reflection coefficient S₁₁ inthe 2-3 GHz frequency range. An antenna with geometry and dimensionssimilar to a standard commercial microwave oven antenna wasmanufactured, and connected to the network analyzer through a 50Ωtransmission line.

In another aspect the invention is directed to a model for highlyefficient thermal MW decomposition of SBC process substrate to producecarbon dioxide (CO₂). This model may be used to specify capsulecontents, apparatus elements and process parameters to control carbondioxide production.

The thermal decomposition reaction of SBC is represented by:2NaHCO₃→Na₂CO₃+H₂O+CO₂  (5)

SBC in solid or powder form has almost no MW absorption property(∈″<10⁻²) and MW alone will not decompose the substrate. Adding water tothe substrate dramatically increases MW absorption, due to added dipolesand dissolved ions, but also decreases the efficiency of substratedecomposition because more MW energy is dissipated on heating waterinstead of substrate.

A semi-empirical physical model based on both theoretical MW powerabsorption coefficients and empirical results relates the thermodynamicsof the thermal decomposition to provide an initial value of SBC:waterratio for each SBC given mass and MW frequency to achieve maximum gasextraction from the thermal decomposition process in the minimum time.

As mentioned above, MW absorption for fixed MW frequency and giveninitial temperature is dependent on water content of the SBC solution.Low water content (<20%) has low dielectric and ionic absorption due tolow dipoles concentration and low ion mobility respectively. While athigh water content (>90%) the dielectric reaches a maximum, the ionconcentration is negligible. As a result, maximum absorption values canbe found at a water content corresponding to highly concentratedsolution. MW absorption as a function of water content presented in FIG.8.

During MW thermal decomposition many thermodynamic properties of the SBCsolution change rapidly. Heating the solution from 20° C. to 100° C.more than doubles SBC solubility and ionic dissipation becomes thedominant mode of MW absorption. CO₂ extraction rate increases by threeorders of magnitude. Thus, decomposition rate is very sensitive totemperature, and to decrease the overall process time, it is crucial toreach the maximum temperature possible.

The thermal energy (Q) needed to heat solution to a desired temperature(on the order of 150° C.), is the sum of the heat energies of thesolution components (SBC and water).Q=m _(SBC) C _(p) ^(SBC) ΔT+m _(w) C _(p) ^(w) ΔT+m _(w) Q _(L)  (6)

where m_(SBC) and m_(w) are the masses of SBC and the waterrespectively; C_(c) ^(SBC) and C_(p) ^(w) are the specific heatcapacities of SBC and water, respectively; ΔT is the temperaturedifference; and Q_(L) is the latent heat of vaporization of water. Thetheoretical estimate for the process total time duration (t) is thequotient of thermal energy needed by the absorbed power.

$\begin{matrix}{t = \frac{Q}{P}} & (7)\end{matrix}$

This time duration has a dependence on water content, increasing mainlyat low and high water content values, because of relative weak solutionMW absorption (FIG. 9).

Initial water content in the capsule is important as it determines thewater balance throughout the remainder of the dynamic process. Presenceof excess water in the heated solution may be detrimental to thereaction, causing a decrease in MW absorption by concentratingabsorption on the water fraction of the solution and unwanted coolingresulting from the formation of steam and/or convection flow inside thesolution. At the same time, low water content will affect processefficiency, impacting ion mobility and preventing thermal energyreaching dry areas of SBC.

Reference is now made to FIGS. 1A and 1B which are schematicillustrations of thermal decomposition system 100 and a partial view100A of system 100 focusing on the capsule chamber 110, respectively.Thermal decomposition system 100 may comprise microwave generator 130;microwave antenna 135 connected to microwave generator 130 and capsulechamber 110.

Capsule chamber 110 may have a sealable opening (not shown) adapted toreceive and hermetically retain at least one capsule 120. According tosome embodiments of the present invention, capsule 120 may comprise athermally decomposable gas source, such as SBC, zeolite and any othermaterials that evolve CO₂ upon thermal decomposition. According to someembodiments, the thermally decomposable material may be in a powderform. According to other embodiments, thermally decomposable materialmay be in a wet powder form. According to yet other embodiments, the wetpowder may be a mixture or a composition of 65%-85% thermallydecomposable material such as SBC, and 35%-15% water. According to someembodiments, the thermally decomposable material to water ratio may be 3to 1.

According to some embodiments of the present invention, capsule chamber110 may withstand, when it is sealed, a defined pressure, for example,of 20 bar, evolving in capsule 120 during operation of system 100.According to some embodiments, capsule chamber 110 may providemechanical support to the outer shell of capsule 120 to prevent ruptureof capsule 120 during operation of system 100 due to the evolvingpressure within

System 100 may further comprise at least one channel 140. According tosome embodiments channel 140 may have a first end 145 a opened to saidcapsule and a second end 145 b connected to a pressure valve 150.

According to some embodiments of the present invention capsule 120 maybe a disposable thin metal capsule 120. According to alternativeembodiments, capsule chamber 110 may be made of an electricallynon-conducting material, virtually transparent to RF energy, which isunderstood to mean that the material blocks less than 1% of RF energy inthe microwave frequency range.

According to some embodiments, when capsule 120 is inserted into capsulechamber 110, capsule 120 may come into electrical contact with microwaveantenna 135. It should be appreciated by those skilled in the art thatwhen capsule 120 is made of metal, capsule 120 may become a disposablemicrowave cavity when in contact with antenna 135 and when RF energy,such as microwave energy, is generated through antenna 135 to capsule120. According to other embodiments of the present invention, capsule120 may comprise a socket 127. Microwave antenna 135 may penetrate,according to some embodiments, through socket 127 into the internalcavity of capsule 120. According to other embodiments, microwave antenna135 may be moveable within the internal cavity of capsule 120 along atleast two axes of a Cartesian coordinate system. It should beappreciated that antenna 135 may be moved during operation of system 100in order to create a homogenous heat distribution within capsule chamber110. It should be further appreciated that when capsule chamber 110 andcapsule 120 have relatively small dimensions, even heat distribution maybe achieved without moving antenna 135. The term “relatively small” inthis case relates to dimensions where the temperature of the contents ofthe chamber has reached a desired level across at least most of thecontent's volume within a defined time period. According to someembodiments, chamber 110 may be movable with respect to antenna 135.Antenna 135 may further comprise at least one microwaveenergy-concentrating element such as sharpened tip to provide very highdensity electric field, which may further contribute to the heatbuild-up. According to some embodiments, the energy-concentratingelement may be adapted to penetrate into capsule 120 through one or morefaces of capsule 120, when capsule 120 is inserted into capsule chamber110.

System 100 may further comprise a pressure transducer 170 to measure andprovide indication of the pressure in internal tube or channel 140.According to some embodiments, pressure transducer 170 may be connectedto or in communication with a control circuit 175 and may transmit tocontrol circuit 175 data regarding the pressure in chamber 110substantially in real time.

According to some embodiments, control circuit 175 may be connected toor in communication with microwave generator 130 to control microwaveenergy by, for example, controlling the frequency generated by generator130, based on the data received from meter 170 and, optionally, basedalso on pre-stored energy absorption behavior curves for several typesof decomposable materials, of several sizes and/or materials ofcapsules, etc.

According to some embodiments, capsule chamber 110 may be made of metalor may have a metal envelope so that capsule chamber 110 may act as amicrowave cavity. According to some embodiments, capsule chamber 110 maycomprise a microwave cavity and may be partially filled with adielectric material.

The microwave cavity may be made of thick aluminum walls, and may bepartially filled with a material substantially transparent to RF energy,such as without limitation Teflon™ (polytetrafluoroethylene), leavingsufficient working space of the microwave cavity. The inner microwavecavity dimensions according to one embodiment of the present inventionmay be 100×60×60 mm in size (360 ml). According to other embodiments,smaller dimensions of microwave cavity may be used. According to someembodiments microwave cavity in capsule chamber 110 may be ahigh-pressure chamber.

Reference is made to FIG. 1C, which schematically depicts high pressurechamber 100B made of a dielectric material and capsule 121B made ofmetallic material and FIG. 1D, which depicts chamber 100C of dielectricmaterial with a chamber inner case made of metal and capsule 121C madeof dielectric material. It may be realized that chamber 110 may be madeof a dielectric material while capsule 120 may be made of a metal andact as a microwave cavity, while according to other embodiments, capsule120 may be made of a dielectric material and chamber 110 may be made ofmetal and act as a microwave cavity. With reference to FIGS. 1A and 1B,according to one embodiment the internal cavity of capsule chamber 110may have a volume of 30-40 milliliter (ml). Capsule chamber 110 maycomprise a microwave antenna slot or socket 115.

According to some embodiments of the present invention, capsule chamber110 may be accessed for filling through side A of chamber 110 (FIG. 1A),for example for inserting a capsule, and may be sealed, for example witha cork (not shown). According to some embodiments, the cork or any othersealing means may be pressed on the Teflon through a silicone O-ring(not shown). It should be appreciated that other sealing means andmethods may be used as known in the art.

According to some embodiments, gasses produced during the decompositionprocess in chamber 110 are vented through an inner tube or channel 140into an external, lower pressure chamber (not shown) through pressurevalve 150.

According to some embodiments of the present invention, this structuremay be designed and built to withstand pressures up to 20 bar andtemperatures up to 250° C. without any observed degradation.

The microwave cavity in capsule chamber 110 may be designed foroperation in its lowest frequency mode, which falls, according to someembodiments, in the range of 2.4-2.5 GHz. According to some embodimentsof the present invention, antenna 135 may be inserted through slot 115in side B of the capsule chamber 110. According to some embodiments,antenna 135 may penetrate through socket 127 of capsule 120 into theinternal cavity of capsule 120.

According to the embodiment depicted in FIG. 1B antenna 135 may notpenetrate into capsule 120 but may come into close proximity to one face121 a of capsule 120. According to some embodiments, face 121 a ofcapsule 120 proximal to antenna 135 may be made of a dielectricmaterial, virtually transparent to microwave energy. According to someembodiments, the remaining faces of capsule 120 may be made of ametallic material.

According to some embodiments, the entire outer skin 121 of capsule 120may be made of a metallic material. According to this embodiment,antenna 135 may come into electric contact with the metallic skin 121 ofcapsule 120, so that skin 121 of capsule 120 may act as a microwaveantenna.

Due to uncertainties in the dielectric constant of the wet powder incapsule 120 and the frequency of microwave generator 130, and due to thevariations of the dielectric constant at varying temperatures, one ormore tuning means may be exercised, as is known in the art, to enableoptimization of the working point (e.g. microwave frequency, location ofthe antenna in the microwave cavity, etc.).

Reference is now made to FIG. 2A which illustrates a system 200according to another embodiment of the present invention. Similar to theembodiments illustrated in FIGS. 1A and 1B, system 200 may comprise acapsule chamber 210, to receive and retain capsule 220. According tosome embodiments, system 200 may further comprise microwave generator230, for example a magnetron, microwave antenna 235 and waveguide 237adapted to direct microwave energy from antenna 235, via capsule chamber210 to capsule 220.

As further seen in FIG. 2A, capsule 220 may be made of metal and mayhave a portion 228 made of a non-conductive material, virtuallytransparent to RF energy.

According to some embodiments, capsule chamber 210 may have a water tubeslot 212 to allow water to be inserted into capsule 220 through a watertube 280. As seen in FIG. 2A, capsule 220 may have an opening 222 toreceive an outlet 285 of said water tube 280.

According to some embodiments of the present invention, capsule chamber210 may comprise an inner tube 240 to vent product gasses, such as CO₂,from capsule 220 to a low pressure chamber (not shown) through pressurevalve 250.

According to some embodiments of the present invention, capsule 220 maycomprise a filter 260 to prevent thermally decomposable materialparticles from being expelled from capsule 220 to channel 240.

With reference to FIG. 2B a different arrangement for transmission of RFpower to the decomposable material is presented. As seen in FIG. 2B, twometal antennas or electrodes 235 a and 235 b placed opposite one anotherare connected to an AC RF energy source 230 at one end, and to oppositesides of microwave cavity 220 at the other end. Apart from thedifference in the arrangement of the RF electrodes/transmitting platesas a microwave source for chamber 220, heating device 200A operatessubstantially similar to heating device 200 of FIG. 2A.

Reference is now made to FIG. 3 which is a schematic illustration of acapsule chamber 310 adapted to receive and retain two capsules 320 a and320 b. As seen in FIG. 3, capsule chamber 310 may have a first area, orspace 310 a and a second area, or space 310 b. According to someembodiments of the present invention the thermal efficiency of themicrowave energy projected into capsule chamber 310 may be unevenlydistributed. For example, the thermal efficiency may be tuned so as toprovide more heating energy to one area, e.g. area 310 a, than thatprovided to another area, e.g. area 310 b. Thus, it should be realizedthat the contents of one of capsules 320 a or 320 b located in the morethermally efficient area of chamber 310 will be heated to a highertemperature than the contents of the other capsule 320 a or 320 b, in agiven time interval and given similar heat coefficient for the contentsof both capsules.

According to some embodiments of the present invention this unevenheating process may be utilized to produce different end products havingdifferent heating requirements in a single operation cycle of highpressure microwave thermal decomposition system (100 in FIGS. 1A and1B). For example, a home appliance for preparing sparkling water andespresso in a single operation cycle may be realized by placing acapsule containing SBC wet powder in an area of chamber 310 where thethermal efficiency is maximal to achieve heating of the SBC wet powderto a temperature at the range of 150° C.-200° C. within 30 seconds, andplacing another capsule comprising grained coffee in an area of chamber310 where the thermal efficiency is low so that during a cycle of 30seconds the grained coffee would not heat to a temperature over, forexample, 90° C. to avoid derogating from the coffee desiredcharacteristics. It would be appreciated that such embodiment may beused to concurrently produce other pairs of products such as carbonatedwater and herbal tea, carbonated water and foamed milk, sparklingbeverages, sparkling yogurt and the like, simultaneously. Providing RFenergy with different heating efficiency to areas 310 a and 310 b may berealized, according to some embodiments, by placing the RF source, e.g.antenna 335, non-symmetrically with respect to areas 310 a and 310 b, sothat the RF induced energy received in one area—e.g. area 310 a, ishigher than that received in area 310 b.

Reference is now made to FIG. 4A which is an embodiment of system 400Aaccording to the present invention. As seen in FIG. 4A, capsule chamber410 may serve as a microwave cavity for pressure heating of a substancecontained in capsule 420. As further seen in FIG. 4A, capsule chamber410 may comprise a water tube 490 passing therethrough. Water tube 490may pass water through capsule chamber 410 and microwave antenna 435 maytransmit RF energy to heat, simultaneously, both the contents of capsule420 and water contained in tube 490. System 400A may further comprisewater tube 492 adapted to penetrate into capsule 420 when it is placedinside chamber 410 and may further be adapted to provide water in orderto wet the contents of capsule 420 when dry powder is used.

With reference to FIG. 4B embodiment of a system 400B is illustrated.The heating of the contents of chamber 410 may be done substantially asdescribed with respect to FIG. 2A. As seen in the embodiment of FIG. 4Bpump 493 and a water source 494 may be connected to via tubing system496 to chamber 410, to pump vented gasses through tube 442, and waterfrom water source 494 back to capsule chamber 410 and into capsule 420in substantially a continuous process.

Reference is now made to FIGS. 5A, 5B, 5C, 5D and 5E which illustrateexemplary capsules 520A-520E, respectively, according to embodiments ofthe present invention. Capsules 520A-D may comprise a closed skin orshell 521 having an internal cavity 522 enclosed in shell 521. Thecapsule of FIG. 5E is a dual capsule adapted to have compartmentspositioned in a first area and a second area in a capsule chamber.

According to some embodiments, capsule 520 may comprise at least a firstcompartment 523 in cavity 522 to comprise a thermally decomposablematerial (not shown), and a filter 560 to prevent particles of thethermally decomposable material from being expelled from capsule 520during thermal decomposition of the material.

According to some embodiments of the present invention, shell 521 may bemade of an electrically non-conductive material, virtually transparentto RF energy. According to other embodiments, shell 521 may be made ofmetal. It should be appreciated by those skilled in the art that whenshell 521 is made of metal shell 521 may be a microwave cavity when incontact with a microwave generator.

According to some embodiment of the present invention, capsule 520 mayrelease carbon dioxide (CO₂) gas which may be released during thermaldecomposition of SBC contained in a compartment of capsule 520.

According to some embodiments of the present invention, capsule 520A maycomprise a socket 524 to receive microwave antenna 535.

According to alternative or additional embodiments, capsule 520D maycomprise microwave energy concentrating elements 525 connected to shell521 and protruding into cavity 522 of capsule 520.

According to some embodiments, socket 524 may be adapted to allowantenna 535 to penetrate into cavity 522 of capsule 520 when capsule 520is inserted into thermal decomposition system (100 in FIGS. 1A and 1B).

According to some embodiments of the present invention, capsule 520B maycomprise a second compartment 526 (in FIG. 5B) to contain a secondsubstance, such as a flavoring substance.

According to some embodiments, capsule 520A may comprise an opening 528covered by a tearable seal 528 a. Opening 528 may be adapted to receivean orifice (145 a in FIG. 1A) of a channel (145 in FIG. 1A) when capsule520 is inserted into system (100 in FIG. 1A). According to someembodiments, capsule 520C may comprise another opening 529, opening 529may be covered by tearable seal 529 a. Opening 529 may be adapted toreceive an outlet of a water tube (280 in FIG. 2A).

FIG. 5E depicts a dual capsule chamber arrangement which is suited toheat different starting materials to a different temperature in capsuleswithin different areas of a capsule chamber. For example, the capsulechamber contains a first compartment 530A containing a first capsule536A and a second compartment 530B containing a second capsule 536B. Thecapsules 536A and 536B are connected by a connecting piece. Thisconfiguration allows the two capsules to be located in separate areas ofthe capsule chamber having respective thermal efficiencies. The firstarea of the chamber may be separated by a wall 532 which inhibitstransmission of RF energy from the first area to the second area, whilethe external chamber housing has metal walls 534 surrounding area 530Bof high thermal efficiency.

According to some embodiments of the present invention capsule 536Acontains a substance that does not get heated, such as flavoring, whilecapsule 536B contains the substance to be heated and thermallydecomposed, preferably a wet SBC powder. The capsule is provided havingtop and bottom seals 560 to maintain the pressure build-up, generateddue to the formation of CO₂, within capsule 536B only. Capsule 536Bfurther comprises a gas exit conduit 562 at the bottom surface of thecapsule to release CO₂.

Reference is made to FIG. 6, which is a schematic flow chart depictingprocess of producing gas by heat, according to embodiments of thepresent invention. Material, such as sodium bicarbonate is provided(block 802) into a heating chamber. The material may be any materialcapable of releasing CO₂ upon thermal decomposition. RF energy isprovided to the material in the chamber (block 804). As the pressure isbuilt inside the chamber due to the release of CO₂, the pressure iscontrolled by a control system to set the process parameters atpredefined values (block 806). According to embodiments of the presentinvention an additional material/liquid may be heated in the heatingchamber (block 810). According to embodiments of the present inventionliquid, such as water, may be circulated through the heated material toimprove absorption of the released gas in the liquid (block 812). Thereleased gas is collected and infused into a liquid reservoir to createa gaseous drink (block 814).

MW susceptor materials in the form of powder, needles and thin films maybe used inside the capsule, or as a component of the capsule, to improvethe efficiency of the thermal decomposition process. Susceptor materialsinclude, without limitation, aluminum flakes, ceramics, metallized filmsand other materials known in the art to exhibit a rapid temperatureincrease in proportion to applied MW power (“susceptance”). Susceptormaterials function as efficient MW absorbers both inside a cavity and inopen space. Thus, adding a susceptor material inside a sodiumbicarbonate-containing capsule or using a susceptor material as acapsule shell may positively increment thermal decomposition processefficiency.

Two principal configurations using MW susceptors are contemplated foruse with the invention: wet capsule and dry capsule. In the wet capsuleconfiguration, adding susceptor elements to the capsule allows forheating of SBC in the vicinity of the susceptor, although the watercontent inside the capsule decreases during the process—which lead tocapsule cooling and a reduction in MW absorbtion (by energy and massoutflow respectively, as described above). The combination of susceptorand water together allows for much faster decomposition rate compared toa capsule containing only water and SBC, without susceptor. In the drycapsule configuration, susceptor elements placed inside the capsuleabsorb MW energy and contribute directly to heating the low absorbingmaterial (such as SBC powder) to enable the thermal decompositionprocess.

EXAMPLE A

A system was built consisting of a small dedicated MW chamber and aconduit exiting the microwave connected to a pressure gauge. A momentaryrelief valve was located on the conduit with the conduit end entering a0.5 L plastic bottle made out of polycarbonate (PC). A dedicated nozzlewas located at the end of the conduit, with a pressure gauge connectedto the bottle, measuring the pressure inside the bottle. A pumpcirculating water in and out of the plastic bottle was connected aswell. The water bottle was filled with water and cooled to a temperatureof 36° F.

The capsule consisted of reusable polytetrafluoroethylene (Teflon) Whichwas filled with 25 g of SBC mixed with 5 cc of water. The capsule wasreceived into the microwave chamber fitting cavity. The microwavechamber was then activated, thus heating the capsule contents.

Simultaneously, the water pump was activated, mixing the waterconstantly. When the heat inside the MW chamber rose, the pressure gaugestarted rising, indicating the production/extraction of the carbondioxide from the capsule. When the pressure inside the microwave chamberreached 15 bar, the valve was opened—allowing the gas to enter thebottle. The pressure inside the bottle rose (indicated by readings fromthe connected gauge). The water circulation caused the gas to bedissolved in the water, thus lowering the pressure inside the bottle.

The process was repeated several times—releasing pulses of carbondioxide into the bottle and mixing them—until the pressure inside themicrowave chamber stopped rising, indicating all the gas contained inthe sodium bicarbonate was released. The full operation duration did notexceed 1 minute.

The soda created inside the bottle was measured using an ICI tester,indicating the GV (Gas Volume) level reached 4.2.

EXAMPLE B

The system of Example A was used for an additional set of experiments,utilizing the same capsule housing but a different ratio of sodiumbicarbonate and water (24 g of obtained Sodium Bicarbonate mixed with5.5 cc of water), and drawing gas in a continuous rather than pulsedsequence.

The water inside the water bottle was cooled to a temperature of 36° F.,and the pump was activated to circulate the water inside the bottle. Themicrowave chamber was then activated, and once the pressure inside thechamber rose to 20bar—the valve was opened, and held open for 40seconds. The soda created inside the bottle was measured using an ICItester, indicating the GV (Gas Volume) level reached 3.1.

While certain features of the invention have been illustrated anddescribed herein, many modifications, substitutions, changes, andequivalents will now occur to those of ordinary skill in the art. It is,therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the invention. Further, the embodiments disclosed herein are related,so that features and dependent limitations disclosed in thespecification in connection with one embodiment or one independent claimmay also be combined with another embodiment or another independentclaim, without departing from the scope of the invention.

What is claimed is:
 1. A thermal decomposition system for carbon dioxideproduction, comprising: a microwave generator; a microwave antennaconnected to said microwave generator; a capsule containing sodiumbicarbonate; a capsule chamber having a sealable opening adapted toreceive and retain the at least one capsule and to withstand a definedpressure evolving in the at least one capsule; at least one channel,said channel having a first end opened to said capsule and a second endconnected to a pressure valve; wherein the microwave generatorconfigured to generate microwave energy applied to said capsulesufficient to cause thermal decomposition of said sodium bicarbonate toevolve carbon dioxide.
 2. The thermal decomposition system according toclaim 1 wherein said capsule is a disposable thin metal capsule and saidcapsule chamber is made of an electrically non-conducting material,virtually transparent to Radio Frequency (RF) energy; and wherein whensaid capsule is inserted into said capsule chamber, said capsule comesinto electrical contact with said microwave antenna to become adisposable microwave cavity.
 3. The thermal decomposition systemaccording to claim 1 wherein said capsule further comprises flavoringsubstance, and wherein said sodium bicarbonate is contained in a firstsection of said capsule and said flavoring substance is contained in asecond section of said capsule.
 4. The thermal decomposition systemaccording to claim 1 wherein said sodium bicarbonate is a wet powdercomprising sodium bicarbonate and water.
 5. The thermal decompositionsystem according to claim 4 wherein said wet powder comprises about 65%to about 85% by weight sodium bicarbonate and about 35% to about 15% byweight water.
 6. The thermal decomposition system according to claim 1wherein said capsule chamber is adapted to receive and retain adisposable capsule made of a non-conductive material virtuallytransparent to RF energy.
 7. The thermal decomposition system accordingto claim 1 wherein said capsule further comprises a filter.
 8. Thethermal decomposition system according to claim 1 wherein said capsulehas a socket; and said antenna is adapted to penetrate into said capsulethrough said socket when said capsule is inserted into said capsulechamber.
 9. The thermal decomposition system according to claim 1wherein said antenna comprises at least one microwave energyconcentrating element adapted to penetrate into said capsule through oneor more faces of said capsule, when said capsule is inserted into saidcapsule chamber.
 10. The thermal decomposition system according to claim1 wherein said capsule is a disposable capsule; wherein a portion ofsaid capsule is made of a material, virtually transparent to radiofrequency (RF) energy; wherein another portion of said capsule is madeof metal; and wherein when said capsule is inserted into said capsulechamber, said portion of said capsule made of a material, virtuallytransparent to RF energy, is proximal to and directed towards saidantenna.
 11. The thermal decomposition system according to claim 8wherein said antenna is movable within said capsule along at least twoaxes of a Cartesian coordinate system.
 12. The thermal decompositionsystem according to claim 1 further comprising: a pressure meter tomonitor the pressure in said capsule chamber; and a control circuit incommunication with said pressure meter and with said microwavegenerator; wherein said control circuit is adapted to change thefrequency and/or the power of microwave energy generated by saidmicrowave generator according to data received from said pressure meter.13. The thermal decomposition system according to claim 1 wherein thecapsule chamber has a first area and a second area; and wherein saidmicrowave generator has a first thermal efficiency in the first area anda second thermal efficiency in the second area, different from the firstthermal efficiency; the microwave generator controllably heatingcontents of the first area to a first temperature and contents of thesecond area to a second temperature, different from the firsttemperature.
 14. The thermal decomposition system according to claim 13,wherein the capsule has a first compartment and a second compartment,the first compartment located in the first area of the capsule chamberand the second compartment located in the second area of the capsulechamber.
 15. The thermal decomposition system according to claim 13,comprising a first capsule located in the first area of the chamber anda second capsule located in the second area of the capsule chamber. 16.The thermal decomposition system according to claim 13, furthercomprising a wall between the first area of the chamber and the secondarea of the chamber, the wall inhibiting transmission of RF energy fromthe first area to the second area.
 17. The thermal decomposition systemaccording to claim 1, wherein the capsule chamber comprises a shell andat least two compartments, at least one of said compartments having ametal wall.
 18. The thermal decomposition system according to claim 1,comprising at least one compartment having a metal wall; saidcompartment having a capsule comprising a top surface, a bottom surface,and containing thermally decomposable starting material said capsulefurther comprising pressure seals to maintain pressure build-up duringthermal decomposition, and said bottom surface of the capsule having agas exit conduit to release produced CO₂.